In the literature, there are three types of demodulation techniques that are currently used in various wired and wireless communications techniques [1], namely, coherent, non-coherent and differentially coherent, which are denoted as CD, NCD and DCD, respectively. Each of the mentioned demodulation techniques is used for particular applications based on the channel and system resources and requirements. Moreover, selecting a particular modulation/demodulation method enables to trade-off the error performance, complexity and spectral efficiency. For example, CD provides low error probability given that the channel state information (CSI) is known accurately at the receiver side. However, accurate knowledge of the CSI requires invoking channel estimation techniques, which might require high complexity signal processing techniques and might affect the system spectral efficiency as well. On the contrary, NCD does not require any information about the CSI hence its a low complexity demodulator, however the error probability is generally very high [2]. DCD is different from CD and NCD because it requires the transmitter to introduce memory in the transmitted sequence. The information symbols extraction does not require the knowledge of the CSI at the received side, however, it requires the CSI to be almost fixed over two consecutive symbols. The probability of error and complexity for the DCD is generally in between CD and NCD. The main disadvantage of DCD is that it requires differential encoding at the transmitter side, and the receiver should know the phase of the first symbol in the received sequence [3], hence it requires some sort of pilot symbols which degrades the spectral efficiency. Moreover, it is very sensitive to phase noise and I-Q imbalance impairments [4]. Therefore, DCD is not suitable for applications where the received signal suffers from phase noise, large phase variations, or time-varying I-Q imbalance.